test: change promises to async/await in test-debugger-backtrace.js
This supersedes https://github.com/nodejs/node/pull/44672 as far as I can tell. FWIW, you can also update/edit an existing pull request without having to open a new pull request. Let us know if we can help! :)
CI: https://ci.nodejs.org/job/node-test-pull-request/46637/
CI: https://ci.nodejs.org/job/node-test-pull-request/46782/
CI: https://ci.nodejs.org/job/node-test-pull-request/46898/
CI: https://ci.nodejs.org/job/node-test-pull-request/46922/
Landed in 19503e746890d04d1dfa24acec9088466bb28d29
Thanks for the contribution! 🎉